1. Technical Field of the Invention
The present invention relates to rake device scraper arms for cleaning screens and perforated screens located in water conduits such as waste water treatment streams, power plants, sewers, and cooling water streams. More particularly, this invention relates to an improved scraper arm to hold a scraper to remove debris from the rake screen or perforated screen without wearing out the rake bar or screen elements.
2. Background of the Prior Art
Bar screens are used for screening solids and debris from flowing liquid streams. An example of such a bar screen system can be found in U.S. Pat. No. 5,730,862 issued to Mahr. In such systems, a series of rakes pass over parallel screen bars, which make up a bar screenfield and remove the debris collected from the flowing stream. Occasionally, large pieces of debris can plug the teeth on the rakes, causing the performance of the rakes to deteriorate. If the rakes do not perform properly, the bars within the bar screenfield can become plugged and eventually cause the water to overflow over the filter system. When this excessive pluggage occurs, the screen system must be cleaned by typically taking the screen system out of service for a relatively long period of time in order to clean the rakes.
Others have attempted to solve the problem of pluggage in the rakes by using such devices as brushes and scrapers to remove debris from the rakes. Brushes get clogged and do not operate very well after a short time period. Others have used scrapers to remove the debris from the rakes. Great Britain Pat. No. GB 1,525,871 issued to Crosby illustrates one example of a scraper. Weaknesses exist in prior scrapers due to the metal-to-metal contact between the scraper and the rake teeth. This metal-to-metal contact causes the scraper to wear out quickly, requiring replacement of the scraper assembly relatively fast.
A need exists for a way of cleaning the rakes within a bar screen system that can be performed quickly, safely, and cost effectively. A need also exists for the cleaning method to be reliable and be able to be used for an extended period of time. Ideally, such a system should be capable of being adapted to the specific fluid applications and also be able to be used on existing screen system equipment with minimal modification.